Metal binders for thermobaric weapons

ABSTRACT

A munition includes a penetrator casing; and a payload, the payload composed of an explosive material dispersed in a metallic binder material. Related methods are also described. A method is also provided that includes forming an energetic material, combining the energetic material with a metallic binder material to form a mixture, and shaping the mixture to form a composite structural munition component.

FIELD OF THE DISCLOSURE

The present disclosure relates to explosive compositions for structuralcomponents of munitions. More specifically, the present disclosurerelates to, at least in part, explosive energetic materials dispersed ina metallic matrix.

BACKGROUND

In the discussion that follows, reference is made to certain structuresand/or methods. However, the following references should not beconstrued as an admission that these structures and/or methodsconstitute prior art. Applicant expressly reserves the right todemonstrate that such structures and/or methods do not qualify as priorart.

While munitions capable of hard target penetration utilize manyspecially designed components and sub-systems to deliver lethal energyto a target, they are substantially comprised of two key elements: 1) awarhead fill which stores and releases explosive energy into a targetwhen triggered, and 2) a penetrator casing that contains the warheadfill and delivers the warhead intact into a hardened target. Manyhardened (or buried) targets, once breached by a penetrator, demonstratea particularly pronounced sensitivity to the blast from thermobaricwarheads in relation to the effect from a high explosive warhead withcomparable explosive energy content. Thermobaric warhead fills aretypically composed of detonable energetic material blends that includehigh explosives, an oxidizer, a dispersed reactive metal power (oftenaluminum), and a polymeric binder that holds the energetic materialstogether. In order to maximize the penetrating capability of a warhead,four primary trades are made involving the shape of the penetrator nose,weight of the penetrator, impact velocity of the penetrator, andcross-sectional area of the penetrator. The achievable depth ofpenetration is considered to be proportional to the weight and to theimpact velocity of the penetrator, but inversely proportional to itscross-sectional area. Often, the impact velocity is limited as in thecase of dropped bombs, and cannot easily be increased for enhanced hardtarget penetration. The overall cross-sectional area of the munition(which includes both the penetrator casing and the energetic fill) canbe reduced to facilitate penetration but a corresponding reduction inwarhead capacity per unit length is then observed. A smallercross-sectional area will also result in a reduced weight/reduced blasttrade unless the weapon is lengthened, which may prevent its use oncurrent and future weapon delivery platforms that have limited weaponstorage capacity. When considering the weight of the penetrator munitionin terms of its volume, the density of a steel alloy penetrator casingis typically 6.5 to 8.5 g/cm³, while the relatively low density warheadfill contained within it is perhaps 1.5-2.5 g/cm³, and the composite, orcombined density falling somewhere in between. If the overall weaponweight per unit volume (i.e., density) were increased thus facilitatingenhanced hard target penetration, and a tailored thermobaric energyrelease produced, hard target lethality can be optimized.

Thus, it would be advantageous to provide an improved munition which mayaddress one or more of the above-mentioned concerns. Relatedpublications include U.S. Pat. Nos. 3,961,576 and 6,679,960, the entiredisclosure of each of these publications is incorporated herein byreference.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a munition whichpossesses one or more of: improved target penetration, improved densitycharacteristics, and improved thermobaric properties.

According to the present invention there is provided a munitioncomprising: a penetrator casing; and a payload, the payload comprisingan explosive material dispersed in a metallic binder material.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The following detailed description of preferred embodiments can be readin connection with the accompanying drawings in which like numeralsdesignate like elements and in which:

FIG. 1 is a longitudinal sectional view of a schematic illustration of amunition formed according to the principles of the present invention.

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a munition 10 formed according to theprinciples of the present invention, and according to one embodimentthereof. The munition illustrated in FIG. 1 can be in the form of aboosted penetrating bomb. The munition 10 may include a penetratorcomprising a casing 12, as well as containing a payload 14, preferablyin the form of an explosive medium. Optionally, a shaped charge liner orcasing insert may be provided within the casing 12 (not shown). Otherpayloads may be used or included, for example, fragmenting bomblets,chemicals, incendiaries, and/or radioactive materials.

As illustrated in FIG. 2, the payload 14 generally comprises a metallicbinder material 20 having a detonable explosive material 30 dispersedtherein.

The binder material 20 can be formed from any suitable metal orcombination of metals and/or alloys. According to one embodiment, thebinder material 20 comprises a metal or alloy that when combined withthe explosive component (or components), the pressure used to compactand densify the structure is of magnitude below that causingautoignition of the explosive materials. According to a furtherembodiment, the binder material 20 comprises one or more of: bismuth,lead, tin, aluminum, magnesium, titanium, gallium, indium, and alloysthereof. By way of non-limiting example, suitable binder alloys include(percentages are by mass): 52.2% In/45% Sn/1.8% Zn; 58% Bi/42% Sn; 60%Sn/40% Bi; 95% Bi/5% Sn; 55% Ge/45% Al; 88.3% AI/11.7% Si; 92.5% Al/7.5%Si; and 95% Al/5% Si. In addition, the binder material 20 may optionallyinclude one or more reinforcing elements or additives. Thus, the bindermaterial 20 may optionally include one or more of: an organic material,an inorganic material, a metastable intermolecular compound, and/or ahydride. By way of non-limiting example, one suitable additive could bea polymeric material that releases a gas upon thermal decomposition. Thecomposite can also be reinforced by adding one or more of the followingorganic and/or inorganic reinforcements: continuous fibers, choppedfibers, whiskers, filaments, a structural preform, a woven fibrousmaterial, a dispersed particulate, or a nonwoven fibrous material. Othersuitable reinforcements are contemplated.

The binder material 20 of the present invention may be provided with anysuitable density. For example, the binder material 20 of the presentinvention may be provided with the density of at least about 6.5 g/cm³,or at least about 8.5 g/cm³, or at least about 10.0 g/cm³. According toa further embodiment, the binder material 20 of the present invention isprovided with a density of about 6.5 g/cm³ to about 8.5 g/cm³, or about6.5 g/cm³to about 14.0 g/cm³.

Component 30 may comprise any suitable explosive material. The explosive30 can be formed from any suitable explosive composition. By way ofnon-limiting example, the high explosive composition can be a suitableexplosive, such as: PBXN-109, PBX-108, PBXIH-135, AFX-757, PBXC-129,HAS-13, RDX, and Tritonal. The volumetric proportion of metal binderwith respect to explosive material(s) may be in the range of 3-60%. Theexplosive material 30 may have any suitable morphology (i.e., powder,flake, crystal, etc.).

The payload 14 of the present invention can be formed according to anysuitable method or technique.

Generally speaking, a suitable method for forming a payload of thepresent invention includes forming an explosive material, combining theenergetic material with a metallic binder material to form a mixture,and shaping the combined explosive material and metallic binder materialmixture to form a payload.

The mixture can be accomplished by any suitable technique, such asmilling or blending. Additives or additional components can be added tothe mixture. As noted above, such additives or additional components maycomprise one or more of: an organic material, and inorganic material, ametastable intermolecular compound, and/or a hydride. In addition, oneor more reinforcements may also be added. Such reinforcements mayinclude organic and/or inorganic materials in the form of one or moreof: continuous fibers, chopped fibers, whiskers, filaments, a structuralpreform, dispersed particulate, a woven fibrous material, or a nonwovenfibrous material. Optionally, the explosive material, the metallicbinder material, the above-mentioned additives and/or theabove-mentioned reinforcements can be treated in a manner thatfunctionalizes the surface(s) thereof, thereby promoting wetting of thecomponent(s) in the matrix of metallic binder. Such treatments are perse known in the art. For example, the particles can be coated with amaterial that imparts a favorable surface energy thereto.

This mixture can then be shaped thereby forming a payload having adesired geometrical configuration. The payload can be shaped by anysuitable technique, such as molding or casting, pressing, forging,machining, cold isostatic pressing, or hot isostatic pressing. Thepayload component can be provided with any suitable geometry.

Alternatively, the mixture may be poured directly into a casing,optionally under a vacuum, and solidified therein.

There are number of potential applications for munitions formedaccording to principles of the present invention. Non-limiting exemplaryweapons and/or weapons systems which may incorporate payloads or payloadcomponents formed according to the principles of the present inventioninclude a BLU-109 warhead or other munition such as BLU-109/B, BLU-113,BLU-116, JASSM-1000, J-1000, and the JAST-1000.

Utilization of a metal binder as described herein as a replacement forpolymeric binders can potentially introduce many attractive ballisticand thermobaric controls on the explosive behavior of the penetratormunition. For example, the metal binders may comprise alloys ofrelatively high density typically in the range of about 6.5 to 14.0g/cm³ (compared to polymeric binders which can be expected to havedensities near 2.5 g/cm³). By replacing currently used polymeric binderswith a metal binder, the overall weapon density will increase resultingin enhanced target penetration capability. Upon initiation of athermobaric blast, metal binder particles will be propelled away fromthe warhead while suspended within the reacting high explosive reactionproducts. Metal binder particles will likely exhibit a desirablenon-ideal behavior due to their high density and large molecular weightsin the blast that lag in velocity (due to momentum effects) andtemperature (due to heat transfer effects) behind the lighter weightgaseous explosive products such as Co, Co_(e), N₂, and H₂O. Thisfavorable non-ideal behavior suggests that the sharpness of theoverpressure peak during the initial blast will be somewhat attenuateddue to thermal and kinetic energy storage of released high explosiveenergy into the ejected metal binder particles. As the blast progresses,release of the kinetic and thermal energy stored in the metal binderparticles will ideally result in an extension of the time atoverpressure and enhanced damage to the target. Metal binders accordingto the present invention have fuel energies comparable to metals burningin oxygen such as zinc, iron, molybdenum, and tungsten, and as such, agiven metal binder may effectively impart a significant afterburningcomponent to the thermobaric blast, further extending the overpressureeffect. Metal binders are compatible with organic materials, inorganicmaterials, reactive thin films, metastable intermolecular composites,hydrides, and combinations of all these energetic materials and areconsidered optional components of the present invention.

To facilitate a uniform dispersion of the explosive metal binder withinthe explosive warhead explosive matrix, the metal particles may bechemically functionalized in such a way that the surface energy betweenthe metal binder particles and the high explosive is minimized promotingwet-out of the metal (if necessary).

Successful implementation of the above approach permits an enhancedtrade-space involving warhead design, achievable hard targetpenetration, and lethality beyond which is available currently. There isreason to believe that implementation of the metal binder will alsoserve to aid in addressing the increasingly present insensitive munitionrequirements imposed on warhead designs.

All numbers expressing quantities of ingredients, constituents, reactionconditions, and so forth used in the specification are to be understoodas being modified in all instances by the term “about”. Notwithstandingthat the numerical ranges and parameters setting forth, the broad scopeof the subject matter presented herein are approximations, the numericalvalues set forth are indicated as precisely as possible. Any numericalvalue, however, inherently contains certain errors necessarily resultingfrom the standard deviation found in their respective measurementtechniques.

Although the present invention has been described in connection withpreferred embodiments thereof, it will be appreciated by those skilledin the art that additions, deletions, modifications, and substitutionsnot specifically described may be made without department from thespirit and scope of the invention as defined in the appended claims.

1. A munition comprising: a penetrator casing having a first density;and a payload, the payload comprising a explosive material dispersed ina metallic binder material having a second density; wherein the seconddensity is at least as great as the first density.
 2. The warhead ofclaim 1, wherein the metallic binder has a density of at least 6.5g/cm³.
 3. The warhead of claim 1, wherein the metallic binder has adensity of about 6.5 to 14.0 g/cm³.
 4. The warhead of claim 1, whereinthe metallic binder material comprises one or more of bismuth, lead,tin, indium, or alloys thereof.
 5. The munition of claim 1, wherein theexplosive material is flaked, powdered, or crystallized.
 6. The munitionof claim 1, wherein the payload additionally comprises one or more of:an organic material, and inorganic material, a metastable intermolecularcomposite, or a metal hydride.
 7. The munition of claim 1, wherein thepayload is reinforced with one or more reinforcements comprising organicor inorganic materials in the form of: chopped fibers, whiskers, astructural preform, a woven fibrous material, a nonwoven fibrousmaterial, or a dispersed particulate.
 8. The munition of claim 7,wherein at least one of the explosive materials, the metallic bindermaterial, and the one or more reinforcements are surface treated topromote wetting.
 9. The munition of claim 1, wherein the munitioncomprises a warhead, and the penetrator casing is at least partiallyfilled with the payload.
 10. A method comprising: forming an explosivematerial; combining the explosive energetic material with a metallicbinder material to form a mixture; and introducing the mixture into theinterior of a penetrator casing.
 11. The method of claim 10, wherein themetallic binder has a density of at least about 6.5 g/cm³.
 12. Themethod of claim 10, wherein the metallic binder has a density of about6.5 g/cm³to about 14.0 g/cm³.
 13. The method of claim 10, wherein themetallic binder material comprises of one more of bismuth, lead, tin,indium, and alloys thereof.
 14. The method of claim 10, furthercomprising adding one or more of the following to the mixture: anorganic material, and inorganic material, a metastable intermolecularcomposite, or a hydride.
 15. The method of claim 10, further comprisingadding one or more reinforcements of organic or inorganic materials inthe form of: chopped fibers, whiskers, a structural preform, a wovenfibrous material, a nonwoven fibrous material, or a dispersedparticulate.
 16. The method of claim 10, further comprising treating thesurface of at least one of the explosive materials, the metallic bindermaterial, and the one or more reinforcements in order to promotewetting.
 17. The method of claim 13, further comprising shaping themixture prior to introducing it into the penetrator casing.